Effects of alcohols on hydrolysis catalyzed by beta-D-glucosidase from Stachybotrys atra.
The interaction of alcohols in the hydrolysis of aryl beta-D-glucopyranosides and aryl beta-D-xylopyranosides by beta-D-glucosidase (beta-D-glucoside glucohydrolase, EC 3.2.1.21) from Stachybotrys atra has been investigated. The results constitute support for the presence of a glycosyl-enzyme intermediate, formed during the first step (glycosylation) of the proposed two-step mechanism. Transfer of the glycosyl group to an alcohol, with the formation of an alkyl glycopyranoside, can take place in parallel to the transfer to a water molecule (second or deglycosylation step). The alcohol binds to the free enzyme and to the glycosyl-enzyme intermediate. The glycosyl-enzyme-alcohol complex undergoes hydrolysis in addition to the alcoholysis. For aryl beta-D-glucopyranosides the deglycosylation step is rate-limiting. For aryl beta-D-xylopyranosides two kinds of substrate behaviour can be observed. Depending on the substituent group on the phenyl ring, either both steps are rate-controlling or the first step is rate-limiting. Electron-withdrawing substituents increase the rate at which the substrate aglycon group is released.
D004305:Dose-Response Relationship, Drug; D000431:Ethanol / Q000494:pharmacology*; D005959:Glucosidases / Q000378:metabolism*; D005960:Glucosides / Q000378:metabolism; D006868:Hydrolysis; D007700:Kinetics; D000432:Methanol / Q000494:pharmacology*; D003904:Mitosporic Fungi / Q000201:enzymology*; D011433:Propranolol / Q000494:pharmacology*; D013191:Stachybotrys / Q000201:enzymology*; D001617:beta-Glucosidase / Q000378:metabolism*
D005960:Glucosides; C025193:4-nitrophenyl beta-D-glucoside; D000431:Ethanol; C031919:4-methoxyphenylglucoside; D011433:Propranolol; D005959:Glucosidases; D001617:beta-Glucosidase; D000432:Methanol